How does a scientist tell if a valcanoe is active or inactive and what is the criteria

see the active volcano paragraph in this:

http://en.wikipedia.org/wiki/Volcano

Thank you!

well they

well they find a way to get close to the valcanoe

To determine if a volcano is active or inactive, scientists use a combination of observations and additional criteria related to its historical eruptions. Here is how scientists typically tell if a volcano is active or inactive:

1. Monitoring Ground Activity: Scientists continuously monitor a volcano's ground activity using various instruments like seismometers to detect seismic activity, GPS sensors to measure ground deformation, and gas sensors to detect changes in gas emissions. These monitoring techniques help determine if there are signs of volcanic activity.

2. Thermal Imaging: Researchers use thermal imaging cameras or satellite-based sensors to detect heat anomalies on the volcano's surface. If there are significant thermal anomalies indicating the presence of hotspots or lava flows, it suggests active magma beneath the volcano.

3. Gas Emissions: Volcanoes release different gases, such as sulfur dioxide, carbon dioxide, and hydrogen sulfide. Measuring and analyzing the composition and volume of gases emitted by a volcano can help scientists understand its activity level. Increasing gas emissions indicate a higher likelihood of volcanic activity.

4. Historical Record: Studying a volcano's eruptive history is crucial in determining its activity level. Scientists examine records of past eruptions, their frequency, and the scale of volcanic events. If a volcano has erupted within the last several hundred years, it is typically considered active, while those that have been inactive for thousands of years are classified as dormant or extinct.

5. Geologic Studies: Scientists study the geological features of a volcano, such as the presence of recent lava flows, volcanic ash deposits, or fresh volcanic rocks. These features provide insights into the volcano's activity history and can help determine if it is currently active or inactive.

It is important to note that classifying a volcano as active, dormant, or extinct is not always straightforward and can be subject to reevaluation based on new data. Volcanic activity is highly variable, and even apparently inactive volcanoes can potentially become active again in the future. Therefore, continuous monitoring and reassessment are crucial for accurate volcano classification.